Thanks for the replies.
Not due it’s MOT yet so unsure about emissions, but your right, my heat shield did rattle over a year ago and I secured it with copper wire, but it’s deteriorated far more now although no rattles yet.
My main concern was , given the internals are being exposed , would the cat get damaged and you both seem to think not.
Might make tentative enquiry to Alex. Don’t think it’s worth replacing them with new ones if their not failing (the cars 15 yr old now) and when they do give up I’m hoping Alex or someone may have some for sale.